Recovery of sulfur dioxid.



JAMES B. German, or rrr'rsnunen. PENNSYLVANIA,'ASSIGNOR ro i/in'rats nnsnaitcn COMPANY, or new roiair, n. at, a CORPORATION or Marian nncovnnr or sutrun nronm.

No Drawing.

To all whom it may concern:

Be it known that l, JAMEs B. GARNER, a citizen of the United States, residing in the city of Pittsburgh, Allegheny county, State of Pennsylvania, have invented certain new and useful Improvements in Recovery of Sulfur Dioxid; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as Will enable others skilled in the art to which it appertains to make and use the same.-

The present invention relates to the con centration and absorption of sulfur dioxid fromgasesinwhich it is contained, as, for instance, the gases given 0d from roasting and smelting furnaces, or derivable from any other source, gaseous, liquid, semi-liquid,

, or solid.

. and absorption of further quantities of sulk closed receptacle, under a pressure lower I The invention is based upon the discovery that animal or vegetable charcoal or coke, prepared in the manner hereinafter described is particularly available for the purpose of concentrating, absorbing, adsorbing, or otherwise taking up and retaining gaseous sulfur dioxid, and that the-sulfur dioxid thus taken up maybe subsequently expelled therefrom as such and recovered in its substantial entirety and'in a condition of great purity. After the expulsion and" recovery of the sulfur dioxid, the charcoal or coke is found to" be again available'for, the recovery fur dioxid, withoutsubstantial diminution of its original efi icacy.

lln carrying'o'ut,the invention, ll may emvegetable charcoal, I have found that box wood charcoal has apparently the highest degree of absorptivecapacity, under the conditions of use, it being capableof taking up as high as 30% by weight of sulfur dioxidl @ther' vegetable 'charcoals,however, are available for the purpose, their selective capacities for the, absorption of sulfur di- OXld from gaseous mixtures difleringsome what in accordance with the varioiis woods from which they are derived. This is true,

not only 'of the usual wood charcoals of commerce, but also of'charcoals from all other woods that are available for charcoal/l manufacture, and, in all cases, the selectivecapacity of the charcoal is decided and considerable,the amount of sulfur dioxid ab Specification of Letters Patent.

. Patented any e, rein Application jfiled December 3, 1914,, Serial No. 875,241.

'sorbable in no case falls below 10% by weight of the charcoal employed. It will be understood, therefore, that the invention, in

ent of a character which, if left in'the charcoal would tend to deposit elemental sulfur within the mass upon the removal of the sulfur dioxid therefrom and would materially decrease the-absorptive power of the charcoal when used in a subsequentcycle. Thus in the case of ordinary charcoal, itmay be prepared for use by either of the two following methods:

First: lln the case of ordinary charcoal,

obtained say from pine wood, or spruce wood, the charcoal is heated in a closed oven in an inert atmosphere; that is to say, for a' period of time which ll prefer shall be about five hours, and at a temperature ranging from 250 G. to 275 C. An atmosphere sufhciently inert is obtained if the oven is' well filled with charcoal and is tightly closed. lit is then permitted to cool to atmosphe'ric temperatures, before removal from the oven, whereafter it is heated in a than atmospheric pressurepreferably a pressure of 7 to 17 millimeters of the mer 'cury column for, say, one-half hour, at a temperatureof from 100 C. to 125 C, whereupon it is permitted to cool for onehalf hour under this pressure, down to at mospheric temperatures, or lower, and is then ready for use.

Secondi The charcoal may be simply heated in a closed receptacle under diminishedpressure, preferably of 7 to 17 mm.

of the mercury column for, say,- one-half hour at a'temperature of 100 C. to 125 C,

Whereafter it is permitted to cool-for onecharcoal from wood by observing during the finishing operations the general conditions above indlcated, a charcoal may be prepared preparation. of any particular charcoal, I

have found that the lower the pressure under which it is heated, for the purposes of the present invention, the more efficient is the charcoal obtained, under like conditions of temperature, and duration of heating. I have also observed that, with difierent charcoals, the time required for driving off the prejudicial occluded gases and volatile ingredients varies somewhat, and it will be understood, therefore, that I do not limit myself to the exact temperatures or pres- Y sures stated, inasmuch as they may be varied within a considerable range, inaccordance with the particular character of the charcoal treated.

The absorption of the sulfur dioxid is preferably effected in the following manner: The gaseous mixture, previously dried, containing the sulfur dioXid, is brought into contact, at, say, ordinary room temperature, 11 C.24A C., with the charcoal or its equivalent, prepared, as hereinbefore described. To this end, it will be found con venient to place the charcoal in a number of receptacles or cells, communicating with each other HISGI'IQS, so that the gaseous mix- I 7 ture-containing the sulfur dioxid maybe within wide limits.

passed through these cells in succession. The sulfur dioxid is found to be completely removed from the gaseous mixture, by passing through the charcoal, even though the rates of;passage, and the concentrations of sulfur dioxi d in the'nliixture are varied A's hereinbefore indicated, the total amount of sulfur dioxid taken up by the charcoal will vary from say 10%"by weight to 30% by weight, according to the charcoal selected, and the efficiency of its treatment. The sulfur dioXid thus takenup by the coke, animal charcoal or vegetable charcoal, as the case may be, can be recovered therefrom in almost its entirety and, in a state of great purity. To this end, without removing the charcoal from the cells in which it has been contained during the taking on of the sulfur are ally from room temperature to 130 this temperature,

ing up of the sulfur dioxid. The temperarises gradu- C. At a small portion of the sulfur dioxid is likewise incidentally driven ture thus employed is one which off. The main body portion of the sulfur is equal to say from 87%9S% and higher,

It will also be according to circumstances. understood that instead of recovering the occluded gases fractionally, as given above, they maybe removed in one operation, in which case the sulfur dioxid so recovered will not be quite as pure as that obtained by the method indicated above.

Instead of heating the cells containing the charcoal at ordinary atmospheric pressure, theymay be heated under a reduced pressure of say 17 millimeters, and the sulfur dioXid recovered in such case has a percentage, of purity within the same range as when heated under atmospheric pressure.

After the sulfur dioxid has been removed by either of the methods specified, the charcoal after cooling in the'cldsed cell is found to be'restored to its original weight, without perceptible. loss, and is the absorption of sulfur further treatment.

Referring again to the temperature at which the sulfur dioXid is absorbed from the gaseous mixture, I would state,that I prefer ordinary temperatures, for the reason that, under working conditions, ordinary temperatures are probably the cheapest to use; although it will be understood that where it is of importance to increase the rapidity of the absorption and to increase the amount of sulfur dioxid absorbed, the temperature may be lowered to advantage. In fact, it has been found that as the temperature is lowered, the rate of absorption and the amount of sulfur dioxid absorbed dioxid, without not only increases, but increases more rapready for reuse, in

absorption should be maintained relatively low, to the advantage of the operation.

The invention is of particular commercial importance for the reason that the process is available for removing from the waste gases of smelters and the like, the sulfur dioXid present even when in a condition of great dilution therein. 7

I do not limit myself to dry gaseous mixtures as indicated above, for while it has been found that dry gases givethe best results, still with wet gases the same general result, witha somewhat lesser efficiency, is obtained."

What I claim is: 1. The method of removing sulfur dioxid from gases containing it, which comprises passing the gases through absorbent carbonaceous material from which have been enema preliminarily expelled such volatile constituents as would tend to deposit in the mass a part of the sulfur dioxid as elemental sulfur; substantially as described.

,2. The method of removing sulfur dioxid from gases containing it, which comprises drying the gases and then passing them through absorbent carbonaceous, material from which have been preliminarily expelled such volatile constituents as would tend to deposit in the mass a part of the sulfurdio'xid as elemental sulfur; substantially as described.

3. The method of removing sulfur dioxid from gases containing it, which comprises passing the gases through absorbent carbonaceous material from which have been preliminarily expelled such volatile constituents as would tend to deposit in the mass a part of the sulfur dioxid as elemental sulfur, and subsequently expelling and recovering the sulfur dioxid taken up; substantially as described. v

4E. The method of removing sulfur dioxid y from gases containing it, which comprises expelling from charcoal by heat the volatile constituents which would tend to deposit therein a part of the sulfur dioxid as elemental sulfur, and passing the gases through the charcoal; substantially as described.

5. The method of removing sulfur dioxid from gases containing it, which comprises contact with the air, and passing the gases through the charcoal; substantially as described. y

7. The method of removing sulfur dioxid fromgases containing it, which comprises expelling by heat from charcoal the volatile constituents which would tend to deposit therein a part of the sulfur dioxid as elemental sulfur, passing the gases through the charcoal, and subsequently recovering the sulfur dioxid therefrom by driving it off by heat; substantially as described.

8. The method of removing sulfur dioxid from gases containing it, which comprises expelling by heat, from charcoal the volatile constituents which would tend to deposit therein a part of the sulfur dioxid as'elemental sulfur, passing the gases through the charcoal, subsequently heating the charcoal at a relatively low temperature to drive offabsorbedimpurities of lower volatility than sulfur dioxid, and finally raising the tefnperature to drive off the sulfur dioxid; substantially as described.

9. The method of removing sulfur dioxid from gases containingit, which comprises passing the gases through charcoal from which has been preliminarily expelled such volatile constituents as would tend to deposit in the mass a part of the sulfur dioxid as elemental sulfur, and subsequently heating the charcoal to a temperature ofabout 180 C. to drive off the sulfur dioxid; substantially as described.

10. The method of recovering sulfur dioxid from gases containing it, which comprises expelling by heat from charcoal the volatile constituents which would tend to deposit therein a part of the sulfur dioxid a's elemental sulfur, passing the gases throu h the charcoal, subsequently heating the c arcoal at temperatures up to about 130 C. to drive off absorbed impurities of lower volatility than sulfur dioxid, and finally raising the temperature to about 180 C. todrive ofi' the sulfur dioxid; substantially as described.

11. The method ,of removing. sulfur dioxid from gases containingit, which comprises passing a current of the gases through an absorbent carbonaceous material and thereby removing the sulfur dioxid there from, and subsequently expelling and r'ecov' ering the thus absorbed 'sulfur dioxid; sub stantially as described.

12. The method of removing sulfur dioxid from gases containing it, which comprises passing a current of the gas through absorbent charcoal and thereby removing the sulfur, dioxid therefrom. L and subsequently heating the charcoal to a suiiicient temperature to'drive 0d the thus absorbed sulfur dioxid'; substantially as described.

13. The method of removing, sulfur di- "oxid from gases containing it, which comprises passing a current of the gases through an absorption receptacle containing absorbent carbonaceous material, and thereby absorbing the sulfur dioxid from such gases,- expelling the thus absorbed sulfur dioxid from such material within the receptacle by heating, and repeating the .process to absorb further amounts of the sulfur dioxid; substantially as described.

14. Themethod of removing sulfur dioxid from gases containing it, which comprises passing a current of the' gases through a series of absorption receptacles containing absorbent carbonaceous material and thereby absorbing the sulfur dioxid from such ases, expelling the thus absorbed sulfur ioxid from such material within the receptacles by heating, and repeating the proc- 'ess to absorb further amounts of the sulfur dioxid; substantially as described.

15. The process of recovering sulfur direc v scribed.

oxid absorbedby charcoal Which'comprises heating the charcoal to a temperature of about 180 (1, and thereby expelling the sulfur dioxid therefrom; substantially as de- 1'6. The process of recovering sulfur dioXid absorbed by charcoal, which comprises heating the charcoal at temperatures up to about 130 C. to drive ofiabsorbed impuri- 10 ties of lower Volatilitythan sulfur dioXid,

JAMES B. GARNER.

VVit-nesses H. H. SMITH, G120. B. NICKEL. 

